Flexible pavements are known to fail in several modes, one of which is rutting. In an effort to determine where in the pavement structure and to what extent rutting occurs and to determine the factors that control rutting, a comprehensive laboratory testing program was performed. Various traffic and environmental parameters were controlled in the study; and from the data, mathematical models that describe the rutting characteristics of an asphalt concrete, a dense graded aggregate, and a subgrade soil were formulated. Details of the materials, equipment, and laboratory procedures were reported by Allen in a previous report. Also, the mathematical models were described in that report and are listed again in this report for convenience. A traffic and a temperature model were also formulated to provide necessary input into the rutting models. These are described in this report.

These models have been programmed and collected into a large computer program entitled PAVRUT. Using this program, an estimated rut depth can be calculated for any flexible pavement, assuming the volume and characteristics of the traffic stream are known.

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The contents of this report reflect the views of the author who is responsible for the facts and the accuracy of the data presented here in. The contents do not necessarily reflect the official views or policies of the University of Kentucky, of the Federal Highway Administration, or the Kentucky Department of Transportation. This report does not constitute a standard, specification, or regulation.